MLA

Firing the Great Gun, or, The Green Bag Open'd [Graphic]. Publd. July 10th, 1820, by Richd. Fores, 71 Leadenhall Street, Aldgate, 0AD. https://collections.library.yale.edu/catalog/33245724.

APA, 6th edition

Firing the great gun, or, The green bag open'd [graphic]. (0 C.E.). [Caricatures and cartoons, Caricatures England 1820, Satires (Visual works) England 1820, Etchings England London 1820, Annotations (Provenance) 19th century, Watermarks (Paper) J. Whatman 1819]. Publd. July 10th, 1820, by Richd. Fores, 71 Leadenhall Street, Aldgate. https://collections.library.yale.edu/catalog/33245724.